Inserts of the first main bearing (from the drive side of the gas distribution system) are larger than the rest of the bearings and both have an oil groove. In the remaining bearings, the liners on the side of the cylinder block have an oil groove, and on the side of the cover they have a smooth surface.
Checking radial clearances
The radial clearance in the main and connecting rod bearings of the crankshaft is measured using special Plastigage measuring rods made of artificial material. Measuring rod laid along the neck (main or connecting rod) and clamped in the bearing is subjected to flattening. The radial clearance in a bearing can be determined (based on the corresponding scale on the packaging of measuring rods) depending on the width of the deformed rod.
Measuring conditions with Plastigage measuring rods:
- necks and liners must be dry and thoroughly degreased;
- the crankshaft must not change its position during the installation and removal of the measuring rods;
- the measuring rod must be laid in half of the liner, at a greater distance from the oil hole in the liner or shaft neck;
- bearing caps must be installed by hand, and their bolts must be tightened to the appropriate torque; you can not strike on the covers;
- tighten only the bearing cap in which the radial clearance is measured; it is impossible to simultaneously measure the clearances in all main bearings.
1. Install the shells on the main bearings in the engine block and install the crankshaft in them.
2. Place the Plastigage dipstick on the first main journal.
3. Install the main bearing cap together with the bushing and tighten the mounting bolts to the correct torque.
4. Carefully remove the bearing cover and use the scale supplied with the measuring rods to measure the width of the deformed measuring rod and, on the basis of the table or graph, determine the radial clearance in the bearing.
5. Compare the measured value with the desired clearance (see subsection 3.2.1.2.4). If the measured gap exceeds the allowable value, repair inserts should be used.
6. In a similar way, measure the clearance in the remaining main and connecting rod bearings.
Axial clearance check
1. After installing the crankshaft in the cylinder block, install the thrust half rings of the crankshaft (oil grooves must be directed outward of the main bearing), bearing caps and tighten them to the appropriate torque.
2. Rest the measuring tip of the dial indicator against the end of the crankshaft and measure its axial clearance.
3. Compare measured values with desired values (see subsection 3.2.1.2.4).If the clearance exceeds the allowable value, repair thrust washers of correspondingly greater thickness should be used.
Checking piston rings and piston clearance in the cylinder
1. After removing the rings from the pistons, measure their clearance in the piston grooves, and after installing them in the cylinders in which they stood earlier, measure the width of the lock (clearance) between their ends (see subsection 3.2.1.2.4).
2. Measure cylinder diameters and piston diameters (in the guide, below the piston pin hole) at right angles to the axis of the piston pin. The piston clearance in the cylinder is equal to the difference between these two measurements.
3. Using a special tool, install the rings on the pistons so that the inscriptions (or designations) were directed towards the bottom of the piston. Place the cuts of the rings at an angle of about 120°.
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